1. Field of the Invention
The present invention relates to a semiconductor device manufacturing method and, more particularly, a semiconductor device manufacturing method having the etching step of an electrode material film constituting a capacitor which has ferroelectric substance or high-dielectric substance.
2. Description of the Prior Art
In recent years, it is concluded that the semiconductor memory employing the ferroelectric capacitor or the high-dielectric capacitor is promising. For example, the ferroelectric capacitor is formed by following steps.
First, as shown in FIG. 1A, the first metal film 102, the ferroelectric film 103, and the second metal film 104 are formed sequentially on the insulating film 101, and then the resist pattern 105 having the capacitor shape is formed on the second metal film 104.
Then, the second metal film 104, the ferroelectric film 103, and the first metal film 102 are etched sequentially by using the resist pattern 105 as a mask. According to this etching, as shown in FIG. 1B, the second metal film 104 is shaped into the upper electrode 104a of the capacitor 106, the ferroelectric film 103 is shaped into the dielectric film 103a of the capacitor 106, and the first metal film 102 is shaped into the lower electrode 102a of the capacitor 106.
Meanwhile, since the first metal film 102 constituting the lower electrode 102a is formed of the noble metal such as iridium, platinum, or the like or its oxide, the first metal film 102 has the poor reactivity at the room temperature and thus is etched mainly by the sputter reaction. As the etching gas in the sputter, mainly the mixed gas consisting of the inert gas such as argon and chlorine is employed.
If such metal film is etched by the sputter reaction, the conductive secure sidewall deposition (fence) adheres to the side surface of the capacitor 106.
Therefore, in order to suppress the formation of the fence, such a structure is employed that the inclination angle of the side surface of the capacitor 106 is set gentle by retreating the side surfaces of the resist pattern 105, otherwise the shape of the capacitor 106 is formed stepwise.
However, if the inclination angle of the side surface of the lower electrode of the capacitor is set gentle or the capacitor is formed stepwise, the size of the capacitor is increased to get the desired capacitance. Therefore, the miniaturization of the semiconductor device having the capacitor is interfered.